1. Field of the Invention
The present invention relates to a communication apparatus, and more particularly to a communication apparatus including one or more remote control (remote-con) transmitters, and one receiver installed inside of a mobile unit, such as an automobile, etc., for selectively controlling and operating a controllable device of the mobile unit, such as a door lock of an automobile, in accordance with switch information, when a variety of switch information transmitted from the transmitter is received by the receiver.
2. Description of the Related Art
A keyless entry apparatus is a known communication system including one or more remote control (remote-con) transmitters and one receiver installed inside of, for example, an automobile. Keyless entry apparatus are used for selectively controlling and operating a controllable device of the automobile (such as the door lock) in accordance with switch control information which is transmitted with identification information from the remote-con transmitters to the receiver.
FIG. 6 is a schematic configuration diagram showing one example of a known keyless entry apparatus which is disclosed in the Japanese Examined Patent Publication No. 7-71337.
As shown in FIG. 6, this keyless entry apparatus consists of, for example, three remote-con transmitters 41-1, 41-2, 41-3, and one receiver 42 installed inside an automobile.
The three remote-con transmitters 41-1, 41-2 and 41-3 respectively include transmission circuit units 43-1, 43-2 and 43-3 for forming transmission signals, identification data storage units (ROM) 44-1, 44-2 and 44-3 for storing identification data R-1, R-2 and R-3 intrinsic to each of the transmitters 41-1, 41-2 and 41-3, and transmitting antenna 45-1, 45-2 and 45-3.
The receiver 42 includes a receiving circuit unit 47 for receiving a transmitted signal through a receiving antenna 46, amplifying the received signal, and wave-shaping the amplified signal, etc., a signal processing unit 48 which is operated in various operation modes corresponding to a variety of control and operation functions of the receiver 42, a storage unit (EEPROM) 49 for storing the identification data R-1, R-2 and R-3, a set-up switch 50 consisting of two switches 50-1, 50-2, for setting the operation mode of the signal processing unit 48, in correspondence with an open/close state thereof, to any of an operation mode, a normal mode, a write mode, and an elimination mode, a door control unit 51 for executing a door lock or a door unlock operation for the automobile, a displaying and informing unit 52 having a light emitting diode and a horn, etc., for signaling a user when the signal processing unit 48 changes from the write mode or the elimination mode to the normal mode, and a timer 53 incorporated into the signal processing unit 48.
The keyless entry apparatus with the above-mentioned configuration operates as follows.
First, the signal processing unit 48 of the receiver 42 is set in the normal mode by switching both switches 50-1 and 50-2 of the set-up switch 50 on the receiver 42 to an open state. In the normal operation mode, when one of the three remote-con transmitters, for example, the remote-con transmitter 41-1, is operated, a door locking or door unlocking operation of the automobile is designated in the transmission circuit unit 43-1 of the remote-con transmitter 41-1, and a control signal (FSK Modulation signal) including the identification data R-1 stored in the identification data storage unit 44-1 is formed, and this control signal is transmitted from the transmitting antenna 45-1 as a radio frequency (RF) transmission signal.
In the receiver 42, when a transmission signal from the remote-con transmitter 41-1 is received by the receiving circuit unit 47 through the receiving antenna 46, the received control signal is amplified and wave-shaped, and then transmitted to the control processing unit 48. First, the signal processing unit 48 compares the identification data R-1 in the received control signal with the identification data R-1 stored in the storage unit 49, and if they are identical, the signal processing unit 48 transmits a control signal to a door lock circuit which identifies a locked state of the automobile door, and then unlocks the door if the door was locked, or locks the door if the door was not locked.
Next, to change the operation mode of the signal processing unit 48 of the receiver 42 from the normal mode to a write mode, that is, for writing the identification data R-1, R-2 or R-3 into the storage unit 49, only one switch 50-1 of the setting switches 50 on the receiver 42 is closed, and the timer 53 is started. If one of three remote-con transmitters, for example, the remote-con transmitter 41-1, is operated immediately after the signal processing unit 48 is switched to the write mode, then a control signal including the identification data R-1 stored in the identification data storage unit 44-1 is formed in the transmitting circuit unit 43-1 of the remote-con transmitter 41-1 and transmitted via the antenna 45-1, and when this control signal is received by the receiver 42, the control signal is transmitted from the receiving circuit unit 47 to the signal processing unit 48, the signal processing unit 48 supplies the identification data R-1 in this control signal to the storage unit 49, and the identification data R-1 is stored in the storage unit 49. When the count value t counted with the timer 53 reaches a predetermined value T, such as 5 seconds, the displaying and informing unit 52 is activated temporarily to notify the user of an operation mode change. Then, after having notified the user of an operation mode change, the operation mode of the signal processing unit 48 is reset automatically from the write mode to the normal mode.
To change the operation mode of the signal processing unit 48 on the receiver 42 side from the normal mode to an elimination mode, that is, when executing a batch elimination (erasure) of the identification data R-1, R-2 and R-3 stored in the storage unit 49, first, only one switch 50-1 of the setting switch 50 on the receiver 42 side is closed, the timer 53 is started, and immediately thereafter, the other switch 50-2 of the setting switch 50 is also closed. When such settings of the switches 50-1, 50-2 are executed, the batch elimination of the identification data R-1, R-2 and R-3 stored in the storage unit 49 is executed, and when the batch elimination of the identification data R-1, R-2 and R-3 is completed, then the displaying and informing unit 52 acts temporarily and after having informed the completion of the elimination of the stored contents in the storage unit 49, the operation mode of the signal processing unit 48 is reset automatically from the elimination mode to the normal mode.
The storage unit 49 has a plurality of storage areas into which a plurality of identification data R are written. During each writing operation, the (k) identification data R are sequentially written into the (k) storage areas of the storage unit 49. However, when the number of identification data R is greater than the number of storage areas (i.e., equal to or greater than k+1), then the initial identification data R is over-written by the new identification data R. For example, the first-entered identification data R-1 is over-written by the identification data R-k+1.
According to the known keyless entry apparatus, when one of the remote-con transmitters, for example, the remote-con transmitter 41-1, is lost, the identification data R-1, R-2 or R-3 intrinsic to all the remote-con transmitters 41-2, 41-3 including that remote-con transmitter 41-1 is typically batch-erased from the storage unit 49 on the receiver 42 in order to maintain high security in the keyless entry apparatus.
In general, when one of the remote-con transmitters, for example, the remote-con transmitter 41-1, is lost, it is necessary to alter the keyless security apparatus so that the remote-con transmitter 41-1 cannot be used to perform a door unlock operation.
The above-mentioned keyless entry apparatus responds to such requirement in a manner that the identification data R-1 of the lost remote-con transmitter 41-1 is eliminated from the storage unit 49, by renewing the identification data R-1 already stored in the storage unit 49, or that the identification data R-1 of the lost remote-con transmitter 41-1 is eliminated from the storage unit 49, by batch-erasing the plurality of identification data R-1, R-2 and R-3 stored in the storage unit 49.
In this case, because it is not known what kind(s) of identification data is (are) stored in what storage area(s) in the storage unit 49, when eliminating the identification data R-1 of the remote-con transmitter 41-1 from the storage unit 49, or the identification data R-1, R-2 and R-3 stored in all the storage areas of the storage unit 49, the above mentioned known keyless entry apparatus must eliminate them by over-writing the identification data R-2 and R-3 of the other remote-con transmitters 41-2 and 41-3, except the identification data R-1.
Incidentally, after having eliminated the identification data R-1 associated with the lost remote-con transmitter 41-1 from the storage unit 49, if the remote-con transmitter 41-1 is subsequently found, in order to enable the keyless entry apparatus to reuse that remote-con transmitter 41-1, the identification data R-1 of the remote-con transmitter 41-1 must be rewritten into the storage unit 49. In a case such as this, even when re-writing the eliminated identification data R-1 into the storage unit 49, regardless of the fact that writing of the identification data R-1 of the remote-con transmitter 41-1 had been previously performed, the above-mentioned known keyless entry apparatus is required to execute a writing of the identification data R-1, R-2 and R-3 of all the remote-con transmitters 41-1, 41-2 and 41-3 including the remote-con transmitter 41-1. Further, when having batch-erased the identification data R-1, R-2 and R-3 of all the remote-con transmitters 41-1, 41-2 and 41-3 from the storage unit 49, in order to make a keyless entry operation at the receiver 42 possible, the above-mentioned known keyless entry apparatus is also required to execute a writing of the identification data R-1, R-2 and R-3 of all the remote-con transmitters 41-1, 41-2 and 41-3 including the remote-con transmitter 41-1.
In this way, the above mentioned known keyless entry apparatus has such a problem that requires a complicated operation of executing a rewriting of the identification data R-1, R-2 and R-3 of all the remote-con transmitters 41-1, 41-2 and 41-3, in order to make the remote-con transmitter 41-1 thereof possible to use again, when the lost remote-con transmitter 41-1 was found, after having altered the keyless entry apparatus such that the lost remote-con transmitter 41(1) is impossible to use.